Possibly Phlebopus marginatus (Giant Bolete)??.... Large Toadstools bursting through clay soil substrate, initially look like "puffball type" but then develop a very thick trunk like stem. No "gills" as yet, smooth brown surface under the Cap, very fast Growth rate, very solid though soft / squishy texture and yellowish inside. The top of the cap has a "cracked / mottled " appearance. Growing in bright sunlight between forbs such as Clustered everlasting Daisy. The size and "trunk" are quite spectacular in size. See size 7 Boot for size reference.